1. Field of the Art
This invention relates to aqueous solutions of acrylamide polymers stabilized against degradation or decomposition.
Acrylamide polymers are being widely utilized in many industrial fields as, for example, sedimentation aids or flocculants, soil conditioners, agents for paper production, additives for electrolytic refining, agents for reducing frictional resistance, textile aids, oil-water separation agents, mobility control agents for enhanced oil recovery, and various binders. Moreover, each time there is a renovation in features such as the types and combinations of the modifications of these polymers, new uses therefor have been developed. Thus, acrylamide polymers are producing successful results in response to expectations on the point of broad use.
However, acrylamide polymers have a serious drawback, whereby the desirable characteristics and capacities inherently possessed by these polymers cannot be amply utilized in some cases. More specifically, acrylamide polymers undergo degradation or decomposition more readily than other polymers. For example, in cases wherein aqueous solutions of acrylamide polymers are left standing at room temperature, a phenomenon wherein the initial viscosity values of these solutions can be maintained for only a short time is frequently observed. This tendency of the performance of these polymers to deteriorate is accelerated particularly at relatively high temperatures, and, in extreme cases, use of polymers for their intended purposes becomes impossible.
Thus, the stabilization of aqueous solutions of acrylamide polymers is of great importance for the reduction to practical use of these polymers which are fundamentally of great value. As a result of the expansion of the fields of use of these polymers, high level of stabilization is being required. For example, an aqueous solution of an acrylamide polymer is used as one of the polymer-augmented waterflooding for enhanced oil recovery. In this case, reservoir temperature is approximately 40.degree. to 100.degree. C., and, moreover, the aqueous solution of the acrylamide polymer is injected for a long time of several months to several tens of months in the underground reservoir extending from the injection well to the production well. Accordingly, the user demands a guarantee for the quantity of the polymer during this period.
Therefore, the suppliers of such acrylamide polymers are faced with the problem of keeping as small as possible variations with time of the polymer quality in this temperature region. When this problem is solved, it will become possible for the first time to amply utilize the original functional worth of these polymers in this field.
2. Prior Art
Various studies have been and are being made for providing agents for preventing degradation of acrylamide polymers. For example, 2-(o-amidophenyl)-2,1,3-benzotriazole and 2-(2-hydroxyphenyl) benzotriazole are introduced as being effective UV absorbers in U.S. Pat. Nos. 3,337,356 and 3,493,539.